Process for the production of low-boiling diolefins



J. P."JONES May .15, 1945. '5

PRocEss FOR THE PRODUCTIQN oF Low-BOILING lDIoLEFINs Filed June 1, 1943 .l Patented A1,945

Pnocass VLo Fon ma PnoDUc'roN oF w-BonmGiDIoLEFINs Y FFIV'CE f Jean lPaul Jones, Bartlesville, Okla., assigner to Phillips Petroleum Delaware Y Company.' a corporation of Application June v1, i943, Serial No. y

-s claims. (ci. 26o- 680) This invention relates to the production of diolefin hydrocarbons from paramn hydrocarbons by dehydrogenation. It relates more particularlyto the production of such dioleflns by means of catalytic dehydrogenation wherein unreacted-hydrocarbons comprising 'par'alns and oleiins are 'recycledto a dehydrogenation step. The inven-v tion hasparticular reference to the production of dioleilns such as butadiene, pentadiene and isoprene from the corresponding paraflln hydrocarbons, preferably by means-of catalytic dehydrogenation. This application is a continuation-inpart of my copending application, Serial No. 404,420, filed July 28,1941.

It has been proposed `to produce diolens by dehydrogenation in a single step wherein a parafiln hydrocarbon such as normal butane is charged to the dehydrogenation step, a diolen such as butadiene is recovered from" the rdehydro'gen'ation eiliuent, and a hydrocarbon fraction containing unreacted hydrocarbons, such as riore efiiuent and returned to the dehydrogenation step. It has also been proposed to produce `diolens from .pal-'ain hydrocarbons by the use of at least two dehydrogenation steps in the iirst of which paraiiins are dehydrogenatedtooleiins and in thesecond of which oleiins are dehydrogneated to diolefins. In suche. process there-is generally avarecycle of unreacted hydrocarbons to oneH or more lof the dehydrogenation steps. In preparing the charge t such dehydrogenation processes it is impossible from a practical point of view to separate a hydrocarbon material such as normal butane in a state of high purity, and in'most incontain a substantial -axount of such -isomerlc hydrocarbons, which do not contribute directly to the Iproduction'ofthe desi-red diolenns.l which i mal butane and butenes., are separated from the tion units 4but also tend to side reactions. As vdiscussed inmy copending application, I-

not only decrease capacity ofthe 'dehydrogenaen'ter into undesired have found that'this tendency for isomerichy drocar-bons to build up in such a dehydrogena-` tion system may be eiiectively kept under control and limited to any desired extent by removing a portion of the recycled .hydrocarbon fraction, separating such isomeric hydrocarbons from this removed portion of the-hydrocarbon-fraction and returning unseparaied -hydrocarbons to the dehydrogenation systemL` In -the process of thepresent inventionl this is accomplished'by subjecting undesired isomeric 'hydrocarbons in the portion so removed to isomerization whereby these undesired hydrocarbons are converted to a desired isomeric form, and returning resultant desired hydrocarbons-to the dehydrogenation system. This procedure .may -be followed either when the undesired isomeric hydrocarbons'are present as a result of formation within the dehydrogenationsystem or when they' are present as a result ojbeing 'included as impurities as a charge to the dehydrogenation system or for any jother reason.

An object of my invention is to' produced# olefin hydrocarbons. 4

It is an object of my invention to produce low'- boiling ldiolen hydrocarbons from paraflin hy-f drocarbons of the same number of carbonatoms per molecule.

' -stances when the particular desired hydrocarbon is. present in a concentration of about 95 per cent A or more, it isconsidered to be in a sufilciently high state oi purity for practical operations. At

times the concentration may even be somewhat lower than 95 percent although generally it will not be appreciably lower than about 90 per cent. Also in such dehydrogenations there is a tendency for isomeric forms of the hydrocarbons being treated to be formed as lay-products in .the dehydrogenation step. T hus, in the dehydrogenation oi' normal butarle and/or normal butenes to j form butadiene, there is a tendency for small amounts of isobutene and isobutane to be formed. When a hydrocarbon fraction containing unreacted hydrocarbonsvis recycled to the dehydrogenation step, it will contain such isomeric hydrocarbons in either case, and as a result after a steady'state of operation has been reached,

the total charge to a dehydrogenation step will It is a further object of my invention to. produce diolen hydrocarbons by means of` catalytic dehydrogenation of more saturated hydrocarbone under conditions such that thereis a 0 minimum formation of undesired by-products.

Further objects and advantages oi' this invention will become apparent from the accompany# ing disclosure and discussion.

My invention will now be described in connection with the accompanying drawing which shows diagrammaticallyby way of a flow sheet a preferred arrangement of apparatus forrpracticing my invention together with certain modiiications thereof. The description oi my invention in connection with the drawing will also serve Ato exemplify-the same.

Rei/erring now to the drawing, a suitable hydro carbon material enters the system through a pipe i0 controlled by a valve i I and is passed to a separating means illustrated by the Iractionating l a valve 2 column I2. Preferably such a hydrocarbon mixture willcomprise predominantly hydrocarbons of a single number of carbon atoms per molecule suchvasa butane fractioncomprising both normal butane and isobutane. or a pentane 'fraction comprising both normal pentane and isopentane. sidered that the material charged through pipe I6 willA be :a butane fraction. 'I'hefractionatlng u column I2 is so operated as to separate a/.normalf butane fraction and an isobutane fraction from through a pipe' I9 controlled by a yalve 2l. A

normal butane fraction of as high a purity as is practical, and preferably containingnormal butane as at least 95 per cent of the mixture. is

removed through a pipe. Il' controlled by a valve Il ,and may bepass'ed througha valve Il directly to a single dehydrogenation unit. Il. The ldehydrogenationunit It is comprised of suitable heating units or furnaces, catalystchambers, and the like, known to the' art for effecting and maintaining catalytic non-destructive dehydrogenation of low-boiling hydrocarbons. The catalyst charn-I bers may be so arranged thatheat issupplied to the catalyst body or bodies and to the reacting mixture. AWhena single dehydrogenation unit is used, the dehydrogenation is conducted to effect a dehydrogenation .bothA of paramns and olefins to form olei'ins and dioleflns, respectivelyfalong', withfree hydrogen. The resulting products passv through a pipe controlled by a valve 2| to separating means 22. Separating means 22 will include suitable fractionating columns. condensing units, heat exchangers. solvent extraction units andthe like suitable for effecting a separation of vthe material chargedinto thedesired fractions as will be'discussed. A diolenn fraction, in .this case containing a high concentration of butadiene. is

`recovered as a product of the process from separating means 22 through a pipe 2l controlled by a valve. 2|. A fraction containing light gases with a high concentration of free hydrogen formed by the dehydrogenation is removed from separating.

means 22 through a pipe 2l and may be discharged at least inpart from the 'system through a valve 2l. Any undesired heavy material may v Y be discharged from the'system through a pipe 2l 'controlled by a valve 2B.

Light hydrocarbons such as Cs and C: hydrocarbons andany' methane not. 'passed through pipe 2l may be discharged through pipe B4.. A recycle fraction, which in this case will comprisefpredominantly normal butane and normal buteneais removed from separating means 22 through 4a pipe 80 and a substantial portion thereof, preferably a predominant porl tion. is passed through valve 8i to be returned lto the dehydrogenation unit Il.

As discussed, this recycle fraction will lcontain 'appreciable amounts of isomeric hydrocarbons. in this case visobutaneand isobutene. In accordance with this modification of the invention, a portion of the recycle' material passing through pipe I0 ispassed therefrom througha pipe I2 and is passed through valve 33 to a hydrogenation unlt'll. .Any undesired portion of 4 this stream maybe discharged i'rom'the-systei'i'i through pipe Il controlled byv 38. Hydrogen-man amount sufilcient to l effect a substantially complete saturation of un` saturated material charged to hydrogenation unit 34 is added to thesystem through a pipe 31'. This For purposes of illustration it will be conhydrogen may be added. entirely or in part through a Vvalve ,but generally there will be more than sulilcient hydrogen in the stream discharged through pipe Illto suffice for this opera- 5 tion, and any desired portion ofthis'stream may be passed from pipe 2l through afpipe con-f trolled by a valve 4 I `to pipe $1 and hydrogenation l. 1 In some instances it may be found more desir- 1" able tofoperate separating means 22 so as Vto separate a fraction containing ,isobutane -and isobutene in higher concentration than would 'otherwls'e be present in the recycle stream passing' the dehydrogenation systemes by being removed from separating; means :22 through pipe 39' and valve". ji o The hydrogenation in unit. will be one oi simple, nondestruc'tive, substantially complete "saturation of unsaturated; hydrocarbons charged thereto 'andmay' be carried outin the presence A 4of'an active hydrogenation catalyst. such as finely 3o divided nickel on an inert support auch as pumice. silica gel, org/the like; under a suitable pressurev Such temperature and presl and temperature, l sure will generally not need to be greatly elevated and conditions for any particular stock beiii!v ing treated may be readily determined by trial by one skilled in nient; j'rhe efnuent or the hy- 'A drogenation is passed from unit 34' through apipe controlled by a valve to a'separating means 4l. Any undesired low-boiling material such as n unreacted free hydrogen and hydrocarbons of a fewer number of'ca'rbon atoms than the material treated inthe dehydrogenation unit I lv may be discharged from the system through a pipe It controlled by a valve '48. A paraffin hydrocarbon fraction .preferably predominantl of a single f number of carbon atoms per-mo ec'ule,`ln this case a butane fraction, is recovered through a Vpipe Il and may he passed through valve 48 directly to pipe i0 and fractionating unit I2. 50 'An lsobutane fraction separated from column l2 is passed'from pipe I3 through pipe`10 and valve '1I to isomerization unit 12 wherein it is contacted with a suitable isomerization catalyst under conditions such as to convert isobutane into normal butane with a minimum of formation of hydrocarbonsof lower and higher molecular weight. A preferred catalyst for such anoperation is aluminum ychloride or bromide'associated withv the corresponding hydrogen halide. 'I'he aluminum chloride, orbromide, may be usedin e. free state or as' e. supported catalyst as is well known lin -the art.V and as may be found most suitable for any particular operation.. A somewhat elevated reaction temperature. .such as in the range of about 200 to 400 F., will favor the production fof normal butane and will permit operation with a' short reaction time. However, such elevated of. undesired by-products, andit will benecessary to limit the reaction time andv also .the extent oi the conversion so that such side reactions do not Y take. place to an extensive extent. Isomerization unit 12 will alsoinclude suitable apparatus for removing hydrocarbon constituents from isomerlzation effluents, and a hydrocrbon stream constantia'lly free of these hydrocarbons, is passed to temperatures are also conducive to the formation.

asvaooi malbutane is removed through pipe ltand re` ,turned to'fractionating column I2 through valve Il.' inthe-concentration oinormal butaneis suf.

high that this material can be subiei'ilied f 'dneeny so ssamm-ensues. it may besessen pipe 'Il through Pille 'Il and valves 18 andy limpios IImrdehydrogensuOn.

In case the butane traction passing through f pipe .l1 a sui'ilciently high concentration ofisobutane. it may be passed directly to isomerisation unit 12 through pipe QI controlled by valve li, hutthis willusually not be a suitable method taining s proportion o: Adesired im. However-.in some instances it. may be mundos.'

sirabie -to have ahighconcentration otioleiins in the material charged to dehydrogenationunit Il. 'In such acase' .separating means ,Il will include suitable' equipment i'or separating o1 from paramos, suchas selective solventextraca tion equipment'as will be readily appreciated by those *skilled in .the.art. -Yaramn hydrocarbons separatedin such a manner may be returned vto dehydrogenation unit I2 as' through .pipell con v, trolied byI a valve Si. AIn some instances with o! operailon unless an iso-C4 concentrate "is charged to hydrogenation unit 34. Isobutane may' `bc-,paased to the System as a charge stock for peyducing butadiene throughpipe II .controlled by valve andthrough pipes Il and Il to imm-.- erisation unit 12. l,

substantially the same procedure may befolwhen converting normal pentane'to piper--y ylenewith substantially the same treatments fof normal Cs and' iso vCs hydrocarbons forthe treat- `meut'discussed for normal C4 and iso C4 hydrooarbons respectively. When converting isopen# tane to isoprene asimilar procedure will be follen either-inodiilca'tionot the dehydrogenation system, material charged through pipe l0 may containsubstantially only hydrocarbons ot a single carbon atom skeleton structure and may in such Y a case constitute-the sole charge tothe process'.

When a fraction containing-'a high proportion o! oleiins suitable for dehydrogenation into dioleis available from any outside sourcesuch a aterial may' becharged to the system through' pipe il when dehydrogenation unit-Il is the 'only part of the dehydrogenation systeme' `When such a charge -is available and adehydrogenation sys'- tem includes both .units B2 and. il, such an oleilncontaining charge may be introduced to the procf ess through pipe t2 controlled by a valve Si pass-y lowed, but' with .conversion of thev isoparamn to the dioleiin and with isomerization of the normal parailln to the isoparaiiin.- Thus isopentanekwill be separated as an overhead product of column Ilthrough a pipe 0I controlled by valve 9i and will Ibe passed through pipe 15 and valve 'Il to the in ier portion oi' pipe Il and to the dehydrogenation system while normalpentane-wili bevpassed a low point o! column i! through pipe l2 controlled by valve Il to isomerization unit 12.

In some instances it may be desired to conduct the dehydrogenation operation in two ormore steps; in such an event the lstream passing through pipe i5 will be passed ere'from through genation unit 52 which as in the case -oi? dehydro-` paraiiinic, and the dehydrogenation .conditions should-besuch that there is an optimum formation o! mono-oleiins oi the same number oi carbon atoms per molecule as the paramos charged.

The dehydrogenation eilluent' is passed through the Vpipe 5t controlled by valve M to separating means It. A fraction containing the desiredl oleiins produced Vbythe dehydrogenation is removed 'from separatingmeansll through a pipe :Il controlled bye-a valve I'I and is passed. back to vpipe filter introductions dehydrosnatlon unit il. -zWith such an operation valve i1 in pipe IB y willbe closed. Undesired low-boiling materials,

including free'h'ydrogen produced bythe @dehydrogenation. may -be discharged from the system pipe-I8 controlled by -.n valve Il passing firomeparating means". Free hydrogen con- 'tained-:inthis stream may be used in thelhydrogenation unit il, and ii'lsuch use is desired' the. :hydrogenmay Aheintrociuced through valve Il- ','aslwili readily appreciated. In some instances -tire.-material passing.` through kpipe-lt will contain; -jjsubstantiallyaii oi' the unreacted parailincharged' -tgxlchydmgenation unit-i2, in which-case-sepa- Mus -mcanssll canbe operated simply to sepaa hydrocarbon iracticur such as a'. butane- `butene Yfraction from lower boiling material.

pipes controlled by a valve bito a dehydrov tion .unit il. and in some instances 'ma charged through pipe l2 may constitute the sole charge to the-process.

' ing into pipes 30 and Il directly to dehydrogena-l 4It has previously been mentioned that thedehydrogenation carried out in units i8 Vand/or 52 will be conducted' under conditions known` to the art and will generally be conductedundera relatively low pressure with or without the presence of diluexit material such as hydrocarbons inert under the dehydrogenation conditions, nitrogen, steam, carbon dioxide and the like.

hydrogen along with the charge to a' catalyst has abenecial efte'ctj especially upon'the initial.

. portion of a catalyst bed before hydrogenis'produced by dehydrogenation, and the presence of such added hydrogen does not retard unduly or upset the dehydrogenation reaction. Such in; troduction can be madefor example. through pipe til and/or pipe 62.- Any of various dehydrogenation lcatalysis may be used, among which the -more preferred are alumina and/or chromium oxide catalysts suchas. bauxite treated with other materials such as yan alkali or alkaline earthv oxide, as bariumoxide, .unglowed chromium oxide, alone or in admixture' with other oxides,

and prepared from a gelatinous chromiumhyl droxide, from carefully controlled, low temperature decompositionof an ammonium chromate,and the like. lSuitable dehydrogenation temperatures will generallybe'found in the' range of 800 to -l300 F. A single stage dehydrogenation, as iirst described in connection with dehvdrogenation unit it, is preferably carried out with a catalyst comprisingl chromium oxide, or chromium oxide', v.and-alumina', at a temperature'in the range of 950 to i100 F. while s. two-stage operation may be carried @out with a similar catalyst' under slightlyless drastic time-temperature conditions in dehydrogenati'onunit B2', with subsequentv de- .hydrogenation of resultant oleilns at *a higher temperature, such as within the range of 1050 to 1250 F.. using -a catalyst such asl bauxite- ,treated with barium hydroxide. or 4temperaturestabilized chromium oxide. with Ior without the, .Dresenee'of steam, or the like. as diluent- In au such dehydrogenation steps-lowpressures, which may be subatmosphericbut which generally will ol' undesired isomerlc hydrocar appreciated. and the normal'butane dehydro genated in separate equipment.

. the dehydrogenation unit or units, and on the isomerizingcharacteristics of the dehydrogenation conditions. With less pure stock and/or appreciable tendencies to form isomerlc hydrocarbons. a .larger portion will need to be passed to the hydrogenation step able conditions. Generallythe amount so treated will be at least about 5 per cent of the total'recycle stream. and while it may be as high as about 25 per cent, it will generally Vbe more economical to modify other conditions to obtain moreravorable operation than to operate so that more than about per cent is so treated. Suitable ratios in any particular case can be rea y dily determined by'` one skilled inthe art.` Ifl rge proportion ns are present in the stream passing through pipe it will be',

desirable to, concentrate these. 'as previously dis Pumps orcompressors for the various streams in connection with the drawing have not been shown; general flow of the various streams, however. has been indicated and discussed, and suitable mechanical equipment for desired-treatment of this material can be readily supplied, as required in any .particular modification of my invennen. by one sinned in the-art.` similarly other units o! equipment have been shown' only diagrammatically but their functions have been r describedand explained so as to serve assuitable guides for adaption of suitable specinc equipment for specific installations.. It will be obvious to' those skilled in the art that various modifications of my invention may bepracticed-asbeing included in the spirit of the disclosure and in the Vscope, of the claims. In the present specification and claims when it is vstated that a portion of a Y stream is removed therefromftheterm "Portion" shalibe understood to means an unfractionated part which has the 'same composition-ag, the stream from which it is removed'.

My invention lsparticularly su duction ofz tHe corresponding' dioleiln. In such a case the products of hydrogenation of the frag- 'tions removed from the recycle stream may be charged to fractionating unit I2 as willbe readily 1.y A process for the production of butadiene. which comprises passing va normal butane Iraption'- to a dehydrogenation zone and effecting a dehydrogenation' thereof forming butadiene.

separating from an effluent of said dehydrogenationa butadiene traction asa product oi the process, separating further a normal C4 fraction substantially .free .from butadiene. comprising Y .predominantlyf normal butane' .-and ynormal butenes and containing a minor amount etico-C4 than with more .favorited to-.the pro- 4 duction of dioleflns such as butadiene, pentadiene.

and isoprene from the corresponding paramn hy'- drocarbons. When a pentane fraction is charged to the system. the products maybe fractionated. `into a normal butane fraction which may be Atreated under cbnditions optimum for the prohydrocarbons, passing a. portion oi said normal Ca fractionl to said dehydrogenation. subjecting a further portion of said normal C4 fraction to nondestructive hydrogenation in the presence of free 2. A process for the production oi butadiene. l

Y which' comprises passing a butane-containing 1s mixture 4to a fractionating means, separating therefrom a normal butane fraction, passing said normal butane fraction to a dehydrogenation zone and effecting a dehydrogenation thereof -ormingv butadiene. separating from an eiiluent of said dehydrogenation a butadiene fraction as a 4product of theprocess, separating also a fraction containing free hydrogen.C further a normal C4 fraction substantially free from butadiene, comprising predominantly normal butane and normal butenes and contain'- dng aminor amount of iso-C4 hydrocarbons, passing a portion of said normal C4 fraction to said dehydrogenation.' subjecting a further portion of saidnormal C4 fraction to nondestructive hydrogenation in the presence of free hydrogen from said fraction containing free hydrogen to form a paraiiinc fraction' containing normal butane .and isobutanel. passing saidparamnic fraction to said iractipnatingmeans.-removing from said 35 iractionating means an isobutanefraction. subjecting said isobutane to isomerization to form normal butane, and passing'normal butane so 1 formed to said zone and effecting a dehydrogenation thereof forming butadiene, separating from an efiluent of said dehydrogenation a butadiene fraction as Aa. product of the process,

tion containing free hydrogen, and separating ,from butadiene, comprising predominantly norm al butane and normal butenes and containins ing a portion or said' normal C; fraction to said dehydrogenation, subjecting a further portion of said normal Cs'fraction to nondestructive hy- .drogenation in the presence of fre'e hydrogen from said fraction containing free hydrogen to form a parai'iinic fraction containing normal butane and isobutane.. passing said parafilnc fraction\ to said fractionating means. removing from said fractionating means an'isobutane fraction. subjecting said is'obutane to isomerization to form a hydrocarbon fractioncontainingnormal eri .butane,.and"passing said hydrocarbon' fraction to said fractionating means. 4. A process for the production of butadiene. 'whieh comprises passing anormal butane frac'- tion to `a `dehydogenationzone andr efiecting'ra separating fro'ni an eiiluent of said dehydrogenation a butadiene fraction asa productor the process, separating'i'urther a normal Cs fraction substantiallyfree irom'butadienel and separating 76 also afraction containingcisobutane andisobuand separating said normal butane traction' to a dehydrogenatlonseparating also a fract iurthe'r a normali@ -fraction substantially free.

minor amount of iso-C4 hydrocarbons'l passdehydrogenation thereof forming butadiene.

asraooi ten`e, passing said normal C4 fraction to said dehydrogenation, subjecting saidiraction contain-v ing isobutane and isobutene to nondestructive hydrogenationin .the presence 0f free hydrogen to form isobutane,l subjecting said isobutane to isomerization to form normal butane, and passing normal butane so formed to said dehydrogenation toform additional butadiene.

, 5. A process for the production of a desired lowboiling diolen of at least four carbon atoms per yntolecule'.- whichl comprises passing a paraiiin hydrocarbon having the same number of carbon drogenation zone and effecting a dehydrogena i tion thereof forming the corresponding dioleiin,

separating from an emuent of said dehydrogenation a diolefln fraction as a product of the process, separating further from said eiiiuent an aliphatic hydrocarbon fraction containing essentially hydrocarbons ofthe same number of carbon atoms per molecule and same carbon atom skeleton structure as said parafiin and desired diolefin and substantially free from dioletin and passing same to said dehydrogenation, separating also from said eiiiuent an olefin-comaining aliphatic hydro- -atoms per molecule and same carbon atom skeleton structure as said desired diolefin to a dehycarbon fraction containing hydrocarbons of a carbon skeleton structure isoniericto said parailin and d`sired dioletln, subjecting said olefin-containing' fraction to nondestructive hydrogenation process, separating also from said eiiiuentga nor-- mal C4 fraction substantially free from butadiene, separating further from said' eiiiuent a fraction containing isobutane and isobutene, separating still further from said eiiiuent a fraction conltaining' free hydrogen, passing said normal C4 fraction to said dehydrogenation, subjecting said fraction containing isobutane and isobutene'to nondestructive hydrogenation in thepresence of free hydrogen from said hydrogen-containing fraction under hydrogenation conditions suitable for forming a completely saturated parainic fraction containing isobutane, subjecting the butane fraction resulting from said hydrogenation to isomerization under isom'erization conditions suitable for converting isobutane to normal butane, .passing the butane fraction resulting from said isomerization to the aforesaid fractionating means, and removing from said fractionating in" the presence of free hydrogen to form a paraiiinic hydrocarbon fraction, subjecting a parailin hydrocarbon from said .paraffinic fraction and isomeric in structure to the iirst said parailin anddesired dioleiin to isomerization to form an isomeric parailin corresponding to the first said paramn and desired diolefin. and passing the last said paramn to said dehydrogenation to form an additional amount 'or said diolefin.

means an isobutane fraction and passing same as an additional charge stock to said isomerization.

7. The process .of claim 5 in which the iirst said paramn hydrocarbon is normal pentane .and pentadiene is produced as a product.

`8. The process Ao1' claim 5 in which the rst 4 said hydrocarbon is isopentane and isoprene is .produced as a product. v

JEAN PAUL JONES.- 

